1. Field of the Invention
The present invention relates to a method and apparatus for the suppression of shock waves, combustion, fragmentation and/or contamination caused by bombs, explosive devices and the like. More particularly, the present invention relates to a method and apparatus which permits on-site disarming, detonation and/or disruption of bombs and/or other explosive devices while reducing and/or eliminating damage to, and contamination of, surrounding areas. More particularly still, the present invention relates to an inexpensive, simple to use and environmentally acceptable blast suppression system which can be quickly and easily mobilized with minimal exposure to a bomb or other explosive device, and which can also be deployed by personnel in protective gear, robots or other remotely-operated devices.
2. Description of the Prior Art
Bombs and other improvised explosive devices have presented a challenge for law enforcement officials for some time. For ease of reference, the term improvised explosive device (“IED”) will be used throughout this discussion. However, it is to be understood that the term IED refers to any bomb or other explosive device, and such term is not intended to be limiting in any manner.
Generally, when an IED, or other suspicious device is discovered, care is taken to avoid moving or otherwise disturbing the IED to prevent premature or inadvertent detonation of the device. Accordingly, a common procedure has been for trained bomb disposal personnel to attempt to disarm such IED's in the location where they are found. However, in many instances, IED's can be quite sophisticated, and trained personnel may not be readily available to deal with the problem. Thus, there is a need for an affordable, efficient and effective means to protect personnel and property from the blast effects of an IED until law enforcement officials can arrive to disarm or otherwise disable the device.
In many instances, the nature of an IED is such that it is not readily capable of being completely disarmed at the site where it is first discovered. In such cases, an attempt is often made to initiate a controlled detonation of the device where it is found by using a smaller explosive charge to detonate the main charge of the IED. In other cases, a smaller explosive charge can be used to deactivate the main explosive device by destroying wires or disabling the primary detonation mechanism of the IED. However, these procedures can also result in unintended detonation of the main device, thereby causing a powerful blast. Thus, there is also a need for an inexpensive, efficient and effective means to protect personnel and property while attempts are being made to disarm or disable an IED.
Generally, damage caused by an IED results from two primary sources: (1) a compression wave or blast; and (2) a fire ball or similar combustion effect. A compression wave is usually a high amplitude, short duration disturbance which moves radially outward from the source of an explosion in all directions. The strength and duration of such wave typically depends on the power and amount of the explosives used in the IED. A fire ball, on the other hand, generally results from ignition of combustible materials in the immediate vicinity of an IED. Both the compression wave and the fire ball/combustion effect of an IED can cause significant damage to the environment surrounding an IED. Accordingly, there is a need for a means to suppress the negative effects of both compression waves and fire balls caused by detonation of an IED.
Additionally, great concern has been expressed regarding radiological bombs or so-called “dirty bombs.” Such devices are essentially conventional explosives which are wrapped in, or otherwise combined with, radioactive materials. Detonation of the conventional explosives causes a blast which has the effect of dispersing such radioactive materials, thereby contaminating the environment around the IED with said radioactive material. Although the blast from the conventional explosives may or may not cause significant damage, contamination of a large or sensitive area with radioactive material can be especially problematic. As such, in addition to suppression of compression waves and/or fire balls caused by detonation of conventional explosives, there is also a need for means to reduce or eliminate the dispersal of radiological and/or other contaminants resulting from detonation of a dirty bomb or radiological device.
Foam has been used for some time to fight fires. More recently, foam has also been used to attempt to control damage caused by IED's. However, such attempts at using foams for this purpose have met with only limited success. Typically, foams used for these purposes are formed from water-soluble surfactants of the perfluorocarbon type which may be dispensed from a variety of different types of equipment. One such foam is known in the art as aqueous film forming foam (“AFFF”). Another type of foam which is well known in the art is so-called “high expansion” foam. Neither of these foams have heretofore proven to be especially effective at controlling blast effects from IED's, especially in formulations commonly used in fire fighting applications.
AFFF foams generally exhibit irregular bubble structures and relatively short drain or “break down” times. By contrast, high expansion foams are primarily designed to produce large quantities of finished foam solution with much greater expansion ratios (up to 1000:1). Such high expansion foams are often used to fill voids and smother conventional Class A fires, such as basement, shipboard and mine fires. These foams frequently produce larger, fragile bubbles which entrap more air, but are extremely susceptible to weather conditions such as wind and rain. The drain or “break down” times of high expansion foams are typically less than fifteen minutes.
Although foams have generally proven to be useful in fighting fires, they have not been entirely satisfactory at suppressing the negative effects associated with IED's. Such foams generally do not have sufficient density and/or strength characteristics to adequately suppress compression waves and/or combustion effects produced by IED's. Moreover, existing blast suppression devices frequently require the use of foam enclosures constructed of high strength and/or blast-resistant material(s) which serve as an additional barrier to dampen blast and/or combustion effects resulting from detonation of an IED. Such enclosures can be expensive, unruly and relatively difficult to handle and install around IED's. Moreover, because such enclosures often require physical manipulation, there is always the possibility that an IED could be inadvertently contacted or otherwise disturbed during the installation process.
Existing blast suppression devices utilizing AFFF and/or high expansion foams also suffer from significant environmental limitations. Many AFFF and high expansion foams are environmentally damaging. As a result, AFFF and high expansion foams can not be used in all settings due to the negative impact that said foams can have on the surrounding environment.
Existing blast suppression systems utilizing AFFF and/or high expansion foams also suffer from other practical limitations related to foam preparation and pumping requirements. Such existing systems frequently require relatively large volumes of water, as well as large foam mixing and/or pumping units which can be unruly and difficult to handle. These requirements can be especially problematic when water supply is limited or when space is an issue, such as when an IED is located indoors.
Pump capacity can also present a problem when an IED is situated above ground level (such as on the upper floors of a multi-story building). In such situations, pumping requirements can often be very significant because the foam creates a significant hydrostatic head which must be overcome. In some cases it may not be possible to pump a required amount of foam from a ground-level mixing unit to an above-ground elevation due to pump limitations. Moreover, in many cases, the foam itself must actually be mixed or prepared at the location where the bomb or IED is discovered, which can take up valuable time and manpower resources.
Thus, there is a need for an affordable blast suppression system which can be quickly and easily deployed to reduce and/or eliminate the negative effects resulting from the detonation of IED's and so-called “dirty bombs.” The blast suppression system should be easily deployed in order to minimize human exposure to an IED or other suspicious device, and utilize flowable foam which is environmentally benign to avoid contamination of the environment in the general vicinity of said device. The blast suppression system should utilize foam that is substantially pre-mixed in order to eliminate the need for large volumes of water and time consuming or labor intensive on-site preparation of such foam. Furthermore, the blast suppression system should be capable of working indoors or in confined spaces, as well as at above-ground elevations.